Judging by reports of Russian troops pouring into the Crimean Peninsula, stories of tense standoffs, sweeping proclamations and alleged deadlines for surrender, the crisis in Crimea is flirting dangerously close to a full scale war. As of Monday evening, there wasn’t a single report of shots fired, but in the history of warfare, past restraint has been a terrible predictor of future action. “War never breaks out wholly unexpectedly, nor can it be spread instantaneously,” famed military theorist Cal von Clausewitz wrote in the early 19th century. “Yet…as soon as preparations for a war begin,” he continued, “the world of reality takes over from the world of abstract thought.”

The reality is grim. It is clear that Russia sees the crisis differently than much of the rest of the world. “The narrative about this in Russia is about protection of the ethnic Russians and the Russian-speaking population,” says Olga Oliker, senior international policy analyst for the Rand Corporation. “It is about stabilizing a country in chaos. It is about a country where, from the Russian perspective, a legally elected president has been deposed by a mob.”

Under those pretenses, Russian troops set about occupying Crimea and now no one knows what will happen next. “If [Russian President Vladimir Putin] is going to occupy a chunk of Ukraine, Crimea would be easier than eastern Ukraine,” Oliker says. The peninsula is self-contained and strategically vital, and the population is predominantly pro-Russian, making it a natural place to halt military operations and press for political gains. But Putin may press further into Ukraine. “If Russia were to actually push further into the country – into central and west Ukraine – it would face a very, very ugly occupation very quickly,” Oliker says. “Over time, an occupation of east Ukraine would also turn ugly.”

Retired U.S. Admiral James Stavridis, the former supreme allied commander of NATO, now the dean of the Fletcher School at Tufts University, wrote a piece in Foreign Policy arguing that NATO needs to develop plans to react to a full-scale invasion of Ukraine and support the ill-prepared Ukrainian military. “Like a chess player leaning forward, [Putin’s] moves are sweeping the board,” Stavridis writes.

Based on the early reports, it’s difficult to detail the composition of Russian forces in Crimea. When troops first appeared, sealing off roads and taking vital airports, they wore uniforms without insignia, but they were well-equipped and quickly swept across the countryside. Ukraine’s envoy at the U.N. claimed on Monday that there were 16,000 Russian troops deployed in Crimea. Over the weekend, Russia conducted military drills near the Ukrainian border with a reported 150,000 troops. According to Russian media, the exercises involved more than 90 aircraft, 120 helicopters, 880 tanks and 80 naval vessels. Mechanized infantry and highly-trained paratroopers conducted maneuvers. “Exercises only show you so much, and they’re almost always reported on afterwards as a tremendous success,” Oliker says. Even taken skeptically, the reports indicate that Russia has enough troops and firepower to easily invade eastern Ukraine.

If Russia continues the invasion, troops will most likely surround Ukrainian garrisons and demand the Ukrainians disarm. Then, there are two likely scenarios. The first is that one side or the other starts shooting, precipitating a full scale war. By most accounts, when Russia invaded Georgia in 2008, the Georgian military made the first move, but the Russians were primed for a provocation.

A similar episode is possible in Ukraine, but Russian troops will be moving to occupy pro-Russian towns and cities near the border. Any airstrikes or use of artillery is unlikely, unless Russian troops meet stiff resistance. Even if they were able to invade Russia-friendly eastern Ukraine without much fighting, the move would exacerbate an already tense situation. “If [Putin] tries to move against the towns and cities along the border in eastern Ukraine, which are all heavily Russian, then we are qualitatively in an entirely new crisis,” says Thomas Nichols, professor of national security affairs at the Naval War College.

Russian’s next move depends on Putin’s broader political goals. If he intends to annex Crimea permanently, he could stay put, or push his forces far enough to establish a de facto annexation of the peninsula. Exclaves are nothing new to Moscow and it retains a form of de facto suzerainty over the breakaway Georgian republics of Abkhazia and South Ossetia. But if Putin intends to dominate the status quo in Ukraine, he could push further into the country. Nichols argues that the U.S., its European allies and NATO have done little to deter Putin’s actions. “Why should he stop?” Nichols asks. “What’s the West policy been so far? ‘Stop, or we’ll say stop again.'”